Topic: was: Re: 62mm Performance Throttle Body

[jonzjeepyj]

I think a stock 2.5L TB is at 48mm and a 4.0L TB is at 58mm
From what I was told that 58-62 is all the stock 2.5 can handle and some
of my friends say that 62mm TB is too large.  The stock intake manifold restricts
air intake after that. I just received my 4.0/58mm TB in the mail today and will put
it on this weekend.

[jonzjeepyj]

Just read on here that the 2.5L TB is 47mm not 48mm
and the 4.0L TB is 53mm not 58mm
47mm-to-53mm is almost a half inch bigger.

John

[Bounty Hunter]

I thought the 4.0L was 55mm, but close enough.

Your friends that say the 62mm TB is too large obviously haven't run one.

[jonzjeepyj]

I don't know if they have but there is always a choke point.  If the stock intake manifold was designed for the stock TB then I'm sure it would handle an increase but at a certain point there wouldn't be any more to gain.  I would like to see the results of stock 2.5TB vs 4.0TB vs 62MM TB on the same vehicle or dyno tested to see if there is any more room for additional performance.

as for the sizes in mm's  I thought it was 48 also but Jeff wrote in another thread the sizes.  Here is the link from this web site...

http://4bangerjp.com/forums/index.php?topic=8.0

Also,  did you bore out the intake manifold or change the air intake to match the bigger TB ?  I know that would make a big difference !

[Bounty Hunter]

The opening in the 2.5L intake manifold needs opened up to 62mm or that is a bottleneck.

[FourbangerYJ]

How does one go about opening up the intake bore?
What size is the intake bore?

[Jeffy]

How does one go about opening up the intake bore?
What size is the intake bore?

Small.  Probably the same as the throat of the TB.  You end up shaving off close to 1/4" around.  What you do is take a new gasket and scribe around the ID.  Then stuff the intake with rags or shaving cream and start grinding with a die grinder or a 2" sanding drum.  Then finish with a flapper wheel.  Vacuum out the shavings and put it back together.

You can sort of see the lip here.

[jonzjeepyj]

I was told that even with the stock 4.0L 54mm TB that you still had to die grind out the intake a bit for it to work properly.  Just curious, I know the power and torque increased.  How did the MPG get effected?  Better or worse?  With the 62mm TB, you won't need as much "pedal" to get the same performance which would equate to a better MPG.  But it's there when you want or need it !

[Jeffy]

I was told that even with the stock 4.0L 54mm TB that you still had to die grind out the intake a bit for it to work properly.  Just curious, I know the power and torque increased.  How did the MPG get effected?  Better or worse?  With the 62mm TB, you won't need as much "pedal" to get the same performance which would equate to a better MPG.  But it's there when you want or need it !

Yes, you will want to bore the hole to the gasket, which is larger then either TB.

I have not done this though. I'm still running a stock 4.0L TB and stock intake manifold as per the original thread.

[FourbangerYJ]

  Then stuff the intake with rags or shaving cream and start grinding with a die grinder or a 2" sanding drum. 

Never heard of the 'Ol shaving cream in the intake trick before. How do you get it out? What stops it from going in to far?

I was thinking either a rag with a lite coat of grease or a ball of tape making sure the fit was real tight with either way. Then shop vac.

I might try a dremel with a rotary rasp. It will be slow but the AL should cut pretty easy.

[Jeffy]

Never heard of the 'Ol shaving cream in the intake trick before. How do you get it out? What stops it from going in to far?

I was thinking either a rag with a lite coat of grease or a ball of tape making sure the fit was real tight with either way. Then shop vac.

I might try a dremel with a rotary rasp. It will be slow but the AL should cut pretty easy.

You can vacuum up the shaving cream, if you can't scoop it out.  Otherwise, it will do no harm if a little gets in there.  Remember you want to keep the hole perfectly round if at all possible.

[FourbangerYJ]

You can vacuum up the shaving cream, if you can't scoop it out.  Otherwise, it will do no harm if a little gets in there.  Remember you want to keep the hole perfectly round if at all possible.

That will be the trick keeping it round. It sounds easy,but leaning over with your arms out holding whatever tool used to ream the hole will get old in a short time.
I think I might give it a try. Prolly not gonna happen until after the new year. I should have the TB by next week or so.

[Bounty Hunter]

I might try a dremel with a rotary rasp. It will be slow but the AL should cut pretty easy.

That's what I used.  Tough to get it perfectly round, clamping a steel guide onto the intake would make it a snap.

[FourbangerYJ]

That's what I used.  Tough to get it perfectly round, clamping a steel guide onto the intake would make it a snap.

How fast did it go?

A scribe line or sharpie wont do for a guide using the gasket for a template?

[Jeffy]

How fast did it go?

A scribe line or sharpie wont do for a guide using the gasket for a template?

Well a metal guide would be best since it wouldn't get ground down and stop you from grinding too much.  Using a 2" drum would keep the hole pretty round and even since it makes a nice arch that will be close to straight.